# Calculate planet's surface temperature by distance from star

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If the planet and star in question are very similar to the Earth and the Sun, how can I calculate the planet's surface temperature by knowing the distance from the star?

This question was originally asked on the Worldbuilding This Site, and someone suggested I ask it here.

Neat and tidy calculations for this aren't possible.

The math behind effective temperature of a planet can be found here and that's a straight forward calculation where you can input distance, solar energy, planet's albedo and get an average temperature. Earth's effective temperature calculation comes to -21 °C, which obviously isn't accurate, but that's as far as the calculation can take you.

Feedback mechanisms:

With essentially no change to distance from the sun, and only relatively small changes in tilt and eccentricity, Earth's temperature can fluctuate from a current 15 °C global average to about 5 °C as it goes in and out of ice ages.

Feedback mechanisms like albedo (ice cover is the key driver, but also deserts, surface area of the oceans), CO2 capture, which increases with colder oceans, can amplify small changes, leading to significant changes in surface temperature. An orbital change, which should account for maybe 1 degree C, or an increase in CO2, which, by itself, captures less than 1 degree C, through feedback mechanisms, can lead to much larger temperature changes.

More on feedback mechamisms here.

Land placement and Ocean circulation

5 or 10 million years ago, Earth's average temperature was about 18-20 °C and that change was driven, primarily, by the closing of the Isthmus of Panama which affected ocean circulation. Just the closing of the Isthmus made ice ages possible. That's a pretty small change in the grand scheme of things, whether your planet has a near equatorial passage where oceans can flow or whether it doesn't, but that one thing can mean more than 10 degrees.

As Antarctica drifted over the south pole (the last 30-35 million years or so) glaciers formed and the earth cooled, because as ice forms, more sunlight is reflected into space and oceans levels drop. Oceans having the lowest albedo and ice the highest. Also, as Antarctica driffs away from the south pole over the next 20-30 million years, Earth is expected to warm, unless another change occurs, like the continued absorption into land and the oceans of CO2.

Earth can only enter an ice age when there's land near the poles. The glacial period of 440-460 million years ago most of the land was over the south pole. The sun was about 4% less luminous and the earth had much more CO2 (though CO2 levels did drop during that time, they didn't drop close to where they are now) and the orbit of the earth, 440 million years ago has some unknowns, but a large land mass over the south pole is thought to have played a key role in making that glaciation possible. The tipping point of ice formation at the poles is particularly sensitive and a significant variable.

So, even with very similar to earth like planets. Just where the land is and how well the oceans circulate and whether the planet can form glaciers and sea ice, or not, can fluctuate perhaps 20 degrees C in global average temperature. How much CO2, how much active volcanism, how much reflective material in the upper atmosphere - all variables.

Even with identical earths, the feedback mechanisms make it difficult to predict what Earth's temperature would be if you pushed Earth 1 million or 1/2 million miles further from the sun. The calculations for surface temperature wouldn't follow a simple mathematical formula. Now, you'd still get colder as you moved the planet away, but one push might give you 1-2 degree and the next push might give you 5-10 and the one after that 0-1. There would be no way to do a clean formula.

## 55 Cancri e: Super-Hot Super-Earth

55 Cancri e is a super-Earth — about twice our planet's size — that zooms around its star in 18 days. It has a surface temperature of nearly 4,900 degrees Fahrenheit (2,700 degrees Celsius). For a while it was dubbed the "diamond planet" because scientists suggested that it was composed of diamonds and graphite. While that theory is not as popular today, the planet still remains an interesting object of study due to its high density and its very close proximity to its parent star. Several follow-up studies have yielded more insights about its super-hot surface, as well as its atmosphere.

## Power output of a star

Stars emit massive amounts of energy per second and so the power of a star is enormous. We assume that a star behaves as a perfectly 'black body' in other words it is a perfect radiator of radiation at its surface temperature.

The Stefan- Boltzmann law states that the power emitted by a black body of surface area A and with a surface temperature T (K) is given by the equation:

Power = σAT 4 where σ is a constant (5.7x10 -8 Wm -2 K -4 ).

(Note: we are assuming here that the temperature of the surroundings (deep space) has a temperature of 0 K)

If we assume that a star is roughly spherical then A = 4πr 2 for a star of radius r.

The power of a star is therefore:

Consider our Sun. It is a star of surface temperature 6000 K, and a radius 6.96x10 8 m. Using the preceding equation we can calculate its power output:

Power output of the Sun = 7.16x10 -7 r 2 T 4 = 7.16x10 -7 x[6.96x10 8 ]2x[6000 4 ] = 7.16x10 -7 x 4.84x10 17 x1.296x10 15 = 4.5x10 26 W

An alternative way of finding out the power output of the Sun is to use the solar constant.

It is interesting to compare this power output with that of Canopus ( a Carinae). Canopus has a surface temperature of 7500 K and a radius of 2x10 11 m. Using these figures it is possible to calculate its power output as being in the region of 9x10 31 W, about 200 000 times greater than that of the Sun!

## How do we know sea level is rising?

You can't just use a ruler to measure global sea level rise. Credit: NASA/JPL-Caltech

Unfortunately, you can't just put a long ruler into the ocean to measure sea level rise. Sea level varies from place to place. This is because of differences in geography, gravity, temperature, ocean currents and tides.

Oceans cover about 70 percent of the world. So, to know how much sea level is rising all over planet, you'd have to have millions of rulers in millions of different places.

It turns out the best way to measure changes in sea level is from space.

This illustration shows the Jason-3 satellite, which measures the distance from itself to the ocean surface by bouncing a beam of radio waves off the water. Credit: NASA/JPL-Caltech

NASA's Jason-3 satellite carries an instrument called a radar altimeter. It uses radio waves instead of a ruler to measure distances.

Here's how it works. Jason-3 bounces radio waves off the ocean surface. The satellite then times how long it takes for these signals to return. Scientists can use this measurement to calculate the distance between the satellite and the ocean surface in that particular location.

Jason-3 orbits about 800 miles (1,300 kilometers) above Earth. Even from that far away, Jason-3 can measure the distance from itself to the ocean surface to within about one inch (about three centimeters).

Jason-3 also has instruments that allow scientists to measure the distance from the satellite to the center of Earth.

By subtracting the first distance (between the satellite and ocean surface) from the second distance (between the satellite and Earth's center), we can calculate the distance from the ocean surface to Earth's center.

The satellite constantly zips over new portions of the planet. In about 10 days, it measures ocean height over the entire Earth. Finding an average of all those measurements gives an average sea level for the whole planet.

During the next 10 days, Jason-3 does it all over again – and again and again, year after year! By seeing how the average distance from the top of the ocean to the center of the Earth increases over time, we can measure how much and how quickly sea level is rising.

## Contents

Planetary surfaces are found throughout the Solar System, from the inner terrestrial planets, to the asteroid belt, the natural satellites of the gas giant planets and beyond to the Trans-Neptunian objects. Surface conditions, temperatures and terrain vary significantly due to a number of factors including Albedo often generated by the surfaces itself. Measures of surface conditions include surface area, surface gravity, surface temperature and surface pressure. Surface stability may be affected by erosion through Aeolian processes, hydrology, subduction, volcanism, sediment or seismic activity. Some surfaces are dynamic while others remain unchanged for millions of years.

Distance, gravity, atmospheric conditions (extremely low or extremely high atmospheric pressure) and unknown factors make exploration is both costly and risky. This necessitates the space probes for early exploration of planetary surfaces. Many probes are stationary have a limited study range and generally survive on extraterrestrial surfaces for a short period, however mobile probes (rovers) have surveyed larger surface areas. Sample return missions allow scientist to study extraterrestrial surface materials on Earth without having to send a manned mission, however is generally only feasible for objects with low gravity and atmosphere.

### Past missions Edit

The first extraterrestrial planetary surface to be explored was the lunar surface by Luna 2 in 1959. The first and only human exploration of an extraterrestrial surface was the Moon, the Apollo program included the first moonwalk on July 20, 1969 and successful return of extraterrestrial surface samples to Earth. Venera 7 was the first landing of a probe on another planet on December 15, 1970. Mars 3 "soft landed" and returned data from Mars on August 22, 1972, the first rover on Mars was Mars Pathfinder in 1997, the Mars Exploration Rover has been studying the surface of the red planet since 2004. NEAR Shoemaker was the first to soft land on an asteroid – 433 Eros in February 2001 while Hayabusa was the first to return samples from 25143 Itokawa on 13 June 2010. Huygens soft landed and returned data from Titan on January 14, 2005.

There have been many failed attempts, more recently Fobos-Grunt, a sample return mission aimed at exploring the surface of Phobos.

Venera 9 returned the first image from the surface of another planet in 1975 (Venus). [4]

The dry, rocky and icy surface of planet Mars (photographed by Viking Lander 2, May 1979) is composed of iron-oxide rich regolith

Pebbled plains of Saturn's moon Titan (photographed by Huygens probe, January 14, 2005) composed of heavily compressed states of water ice. This is the only ground-based photograph of an outer Solar System planetary surface

Surface of comet Tempel 1 (photographed by the Deep Impact probe), consists of a fine powder of contains water and carbon dioxide rich clays, carbonates, sodium, and crystalline silicates.

The most common planetary surface material in the Solar System appears to be water ice. Surface ice is found as close to the Sun as Mercury but is more abundant beyond Mars. Other surfaces include solid matter in combinations of rock, regolith and frozen chemical elements and chemical compounds. In general, ice predominates planetary surfaces beyond the frost line, while closer to the Sun, rock and regolith predominate. Minerals and hydrates may also be present in smaller quantities on many planetary surfaces.

### Rare surface occurrences Edit

Surface liquid, while abundant on Earth (the largest body of surface liquid being the World Ocean) is rare elsewhere, a notable exception being Titan which has the largest known hydrocarbon lake system while surface water, abundant on Earth and essential to all known forms of life is thought only to exist as Seasonal flows on warm Martian slopes and in the habitable zones of other planetary systems.

Volcanism can cause flows such as lava on the surface of geologically active bodies (the largest being the Amirani (volcano) flow on Io). Many of Earth's Igneous rocks are formed through processes rare elsewhere, such as the presence of volcanic magma and water. Surface mineral deposits such as olivine and hematite discovered on Mars by lunar rovers provide direct evidence of past stable water on the surface of Mars.

Apart from water, many other abundant surface materials are unique to Earth in the Solar System as they are not only organic but have formed due to the presence of life – these include carbonate hardgrounds, limestone, vegetation and artificial structures although the latter is present due to probe exploration (see also List of artificial objects on extra-terrestrial surfaces).

#### Extraterrestrial Organic compounds Edit

Increasingly organic compounds are being found on objects throughout the Solar System. While unlikely to indicate the presence of extraterrestrial life, all known life is based on these compounds. Complex carbon molecules may form through various complex chemical interactions or delivered through impacts with small solar system objects and can combine to form the "building blocks" of Carbon-based life. As organic compounds are often volatile, their persistence as a solid or liquid on a planetary surface is of scientific interest as it would indicate an intrinsic source (such as from the object's interior) or residue from larger quantities of organic material preserved through special circumstances over geological timescales, or an extrinsic source (such as from past or recent collision with other objects). [6] Radiation makes the detection of organic matter difficult, making its detection on atmosphereless objects closer to the Sun extremely difficult. [7]

Examples of likely occurrences include:

– many Trans Neptunian Objects including Pluto-Charon, [8] Titan, [9] Triton, [10]Eris, [11]Sedna, [12] 28978 Ixion, [13] 90482 Orcus, [14]24 Themis[15][16] (CH4·5.75H2O) – Oberon, Titania, Umbriel, Pluto, 90482 Orcus, Comet 67P
##### On Mars Edit

Martian exploration including samples taken by on the ground rovers and spectroscopy from orbiting satellites have revealed the presence of a number of complex organic molecules, some of which could be biosignatures in the search for life.

##### On Comet 67P Edit

The space probe Philae (spacecraft) discovered the following organic compounds on the surface of Comet 67P:. [24] [25] [26]

### Inorganic materials Edit

The following is a non-exhaustive list of surface materials that occur on more than one planetary surface along with their locations in order of distance from the Sun. Some have been detected by spectroscopy or direct imaging from orbit or flyby.

( H
2 O ) – Mercury (polar) Earth-Moon system [27] Mars (polar) Ceres[28] and some asteroids such as 24 Themis [29] Jupiter moons – Europa, [30]Ganymede and Callisto Triton, [31] Saturn moons – Titan and Enceladus Uranus moons – Miranda, Umbriel, Oberon Kuiper belt objects including Pluto-Charon system, Haumea, 28978 Ixion, 90482 Orcus, 50000 Quaoar rock – Mercury, Venus, Earth, Mars, asteroids, Ganymede, Callisto, Moon, Triton – Mercury [32] Venus, [33] Earth-Moon system Mars (and its moons Phobos and Deimos) asteroids (including 4 Vesta[34] ) Titan ( N ) – Pluto–Charon, [35]Triton, [36]Kuiper belt objects, Plutinos ( S ) – Mercury Earth Mars Jupiter moons – Io and Europa

#### Rare inorganics Edit

– Earth, Mars, Ceres, Europa and Jupiter Trojans, [37] Enceladus [38] – Earth Mars [39] asteroids including Ceres [40] and Tempel 1 [41] Europa [42] – Earth, Mars, Titan ( CaCO
3 ) – Earth, Mars [43][44] ( Na
2 CO
3 ) – Earth, Ceres [45][46][47]
##### Carbon Ices Edit

Common surface features include:

(though rarer on bodies with thick atmospheres, the largest being Hellas Planitia on Mars) as found on Venus, Earth, Mars and Titan and cryovolcanoes (the highest being Rheasilvia on 4 Vesta) [citation needed]
• Canyons and valleys (the largest being Valles Marineris on Mars) , found on Venus, Earth, The Moon and Mars

Normally, gas giants are considered to not have a surface, although they might have a solid core of rock or various types of ice, or a liquid core of metallic hydrogen. However, the core, if it exists, does not include enough of the planet's mass to be actually considered a surface. Some scientists consider the point at which the atmospheric pressure is equal to 1 bar, equivalent to the atmospheric pressure at Earth’s surface, to be the surface of the planet.[1]

## Three Earth-Size Planets Found Orbiting a Nearby Ultracool Star

The search for Earth-like planets continues, as astronomers scour the sky examining stars for telltale clues of orbiting worlds. Most of the exoplanets found are big, like Jupiter, because they’re the easiest to detect. But our technology has become better and more clever over the years, and smaller planets have been found, including many roughly the size of Earth.

That search took a cool turn this week … literally. A team of astronomers announced they have found not one but three Earth-size planets orbiting a red dwarf, a tiny and cool star just 40 light-years away!

This is very interesting for many reasons: This is the lowest mass full-fledged star ever seen to have planets, it’s relatively close by, and all three planets are (more or less) in the star’s “habitable zone,” where temperatures might—might—support the existence of liquid water on the planets’ surfaces.

The European Southern Observatory put together a nice video explaining this, so give it a view:

The planets were discovered using TRAPPIST (short for Transiting Planets and Planetesimals Small Telescope). This is a 60 cm (24”) telescope that takes images of a select group of 60 nearby red dwarf stars visible from the Southern Hemisphere. The team looks for dips in the stars’ light that are caused by any planets orbiting those stars periodically blocking their host star’s light this is called the transit method, and most exoplanets have been discovered this way.

TRAPPIST found evidence of planets orbiting a star, called TRAPPIST-1, and follow-up observations were made with much larger telescopes. Three planets were found in total, which is remarkable all by itself. But it gets better.

TRAPPIST-1 is an M8 dwarf, only 0.08 times the mass of the Sun just barely massive enough to fuse hydrogen into helium in its core. If it were much lower mass we wouldn’t call it a star at all (we’d say it’s a brown dwarf). Its surface temperature is only about 2,550 K—the Sun is literally more than twice as hot—so it’s informally called an “ultracool” star. And it’s tiny, only about 0.11 times the diameter of the Sun. That’s roughly the same size as Jupiter!

Yet this teeny star sports at least three planets. Called TRAPPIST-1b, c, and d, the exoplanets were detected as they blocked a small fraction of the star’s light. The sizes of the planets were found by seeing just how much of the starlight they blocked. The best measurements indicate they are 1.1, 1.05, and 1.2 times the size of Earth. We don’t know their masses, but if they have the same composition as our home world—rock and metal—then their surface gravities wouldn’t be all that different than ours.

So they’re Earth-size. But are they Earth-like? That is, nearly the same temperature and composition as Earth?

We have no idea what these planets are made of. They could be rock, metal, watery, airless … with our current technology we don’t know how to determine that. Finding the masses of these planets would be extremely difficult, so we’re out of luck there.

But we can estimate their temperatures. The temperature of a planet depends on its distance from the star and that star’s temperature, of course, but also on how reflective the planet is a more reflective planet will be cooler than a dark, absorptive one.

Each of the planets orbits ridiculously close to the star compared with the planets in our solar system. In order, they’re 1.7 million, 2.3 million, and 3.3 million–22 million kilometers from the star (the observations of the third planet, d, don’t constrain its distance very well, so there’s a range of possible distances). Mind you, Mercury is 58 million kilometers from the Sun, so all three of these planets would easily fit inside Mercury’s orbit, with a tens of millions of kilometers to spare.

But remember, the star is very cool, so even at those distance the planets aren’t as hot as you might think.

Assuming very dark planets, the inner two would be about 125° and 70° C, far too hot for life as we know it. The outer planet’s distance from the star wasn’t as well determined, but it would likely have a temperature somewhere from -160° - +10° C depending on its distance. The warmer end of that range is close to Earth’s average temperature!

Remember, that’s assuming dark planets. If they’re more like Earth (which reflects about 40 percent of the light that hits it), they’ll be cooler. If they’re reflective enough, the inner two planets might be more like Earth, too (but the outer planet would be a frozen ball of ice).

That part is more speculative we have no idea how reflective they are. It’s possible, though I’d think unlikely, that all three planets are somewhat clement.

Again, we don’t know much about them they might be airless, or have thick atmospheres of carbon dioxide, or some other noxious combination, so don’t start looking into real estate on them just yet. And even if they are Earth-like, 40 light-years is 400 trillion kilometers. That’s a fairly long road trip. It would take 450 million years to drive there at highway speeds. Better pack a lunch.

But don’t be disappointed. The amazing thing to remember here is that these planets exist at all. Even dinky red dwarf stars manage to make planets, including ones the same size as ours. That’s incredibly exciting.

Another reason this is so exciting is because of the host star. Cool red dwarfs are faint and hard to detect, making these observations somewhat difficult, but they also make up the most populous class of star in the galaxy. If they have planets in the same proportion as more massive, hotter stars do, then planets orbiting red dwarfs will outnumber planets orbiting all other types of stars combined. And here we found three Earth-size planets orbiting one nearby.

It’s impossible not to ask, how many planets like Earth exist in the galaxy? We’re not sure, but various methods have been used to estimate that number, and even conservatively their numbers must be in the billions. Billions. In our galaxy alone.

And our tech is getting better. In the coming years we’ll have telescopes able to dissect the light from such planets, looking for the Earth-like conditions: oxygen in the atmosphere, say, and a temperature more like ours. We’ve found a few candidates for Earth-like exoplanets, but nothing yet that we can point to and confidently say, “Earth 2.”

## Contents

Size comparison of Kepler-452 b with Earth. Kepler-452b has a probable mass five times that of Earth, and its surface gravity is nearly twice as Earth's, though calculations of mass for exoplanets are only rough estimates. If it is a terrestrial planet, it is most likely a super-Earth with many active volcanoes due to its higher mass and density. The clouds on the planet would be thick and misty, covering much of the surface as viewed from space.

The planet takes 385 Earth days to orbit its star. Its radius is 50% bigger than Earth's, and lies within the conservative habitable zone of its parent star. It has an equilibrium temperature of 265 K (−8 °C 17 °F), a little warmer than Earth.

### Host star

The host star, Kepler-452, is a G-type and has about the same mass as the sun, only 3.7% more massive and 11% larger. It has a surface temperature of 5757 K, nearly the same as the Sun, which has a surface temperature of 5778 K. The star's age is estimated to be about 6.5 billion years old, about 1.9 billion years older than the Sun, which is 4.6 billion years old. From the surface of Kepler-452b, its star would look almost identical to the Sun as viewed from the Earth.

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 13.426 therefore, it is too dim to be seen with the naked eye.

### Orbit

Kepler-452b orbits its host star with an orbital period of 385 days and an orbital radius of about 1.04 AU, nearly the same as Earth's (1 AU). Kepler-452b is most likely not tidally locked and has a circular orbit. Its host star, Kepler-452, is about 20% more luminous than the Sun (L = 1.2 L ).

## Calculate planet's surface temperature by distance from star - Astronomy

An extrasolar planet, or "exoplanet", is any planet that orbits a star other than the Sun. We know of exoplanets of all sizes, from bigger than Jupiter to smaller than Earth. Just like in our Solar System, exoplanets can orbit their stars at any distance some exoplanets orbit so close to their stars that their surface temperatures are hot enough to melt iron! Some exoplanets will orbit at just the right distance that we say they're in their star's "habitable zone", that they are the right temperature to have liquid water at their surface and might be able to support life.

Exoplanets are difficult to see directly from Earth. Because they are so small and faint, they are easily lost in the glare of the bright stars they orbit, so we often use indirect methods to find them. One of these is called the "transit method", where we carefully measure the brightness of a star over a long period of time, and look for periodic decreases in the brightness of a star that are caused by a planet passing in front of it. The MEarth Project uses the transit method to look for planets.

Stars come in all sizes. Most of the stars in the Galaxy are stars much smaller than the Sun, stars that astronomers call "M dwarfs." If we're looking for planets by measuring how much of their stars' light they block, then small stars like M dwarfs are great places to look: the same size planet will block a larger fraction of the light from an M dwarf than it would of a larger star like the Sun. M dwarfs are also much cooler in temperature than the Sun, so a planet with the right temperature for life will orbit an M dwarf more closely and be more likely to pass in front of it, as seen from our telescopes.

So, by focusing our efforts on M dwarf stars, we improve our chances of finding Earth -like planets - that's how we got our name, the MEarth Project!

After we find an exoplanet with MEarth, how can we learn more about it? One kind of observation we can make is called "transmission spectroscopy." When a planet passes in front of its star, a tiny fraction of the star's light passes through the planet's atmosphere before reaching us. By very carefully measuring the color of this light (which we call the transmission spectrum), we can learn about what molecules make up the planet's atmosphere. When we make these measurements, it's like we're watching sunset on a different planet!

If we find a potentially habitable planet with MEarth, the next generation of big telescopes like the 6.5 meter James Webb Space Telescope or the 24.5 meter Giant Magellan Telescope will help us study the composition of its atmosphere. But we have to find the planet first!

Click the image at right to find more about the science involved in the MEarth Project. This is a copy of a recent MEarth poster presented at the May 2014 conference on "Habitable Worlds Across Space and Time" at the Space Telescope Science Institute in Baltimore, MD.

## Scorching-hot planet candidate spotted around famous star Vega

Astronomers have spotted a possible searing-hot planet orbiting Vega, one of the brightest and most famous stars in the sky.

The candidate alien planet, which still needs to be confirmed by follow-up observations or analyses, is roughly the size of Neptune and lies very close to Vega. It takes only 2.5 Earth days for the purported planet to make a single orbit around its sun.

Thanks to that proximity, the candidate planet's surface temperature is probably around 5,390 degrees Fahrenheit (2,976 degrees Celsius), researchers calculated. That would make it the second-hottest planet known, if it does indeed exist. (The hottest, KELT-9b, is a whopping 7,800 degrees Fahrenheit, or 4,300 degrees C.)

Vega lies a mere 25 light-years from Earth and sits relatively high in the northern sky, so follow-up studies of this potential planetary system are a real possibility. Scientists will seek to confirm the Neptune-size world and also hunt for other possible planets around the famous star, which is in the constellation Lyra.

&ldquoThis is a massive system, much larger than our own solar system," Spencer Hurt, the lead author of a new study announcing the Vega candidate planet, said in a statement.

"There could be other planets throughout that system," added Hurt, an undergraduate astronomy student at the University of Colorado, Boulder. "It's just a matter of whether we can detect them."

Team members spotted the candidate planet after looking at about 10 years of data collected by the Fred Lawrence Whipple Observatory in Arizona. They saw a slight wobble in the star's motion, suggesting that an orbiting planet is tugging on it gravitationally.

Astronomers have been hunting for planets around Vega for many years. Back in 2013, astronomers announced evidence of a huge asteroid belt circling the star and expressed hope that the find may eventually lead the way to spotting planets. The discovery team added, however, that confirming planets may have to wait until after the launch of NASA's powerful James Webb Space Telescope, which is scheduled to launch this October.

That said, Vega is so bright that professional telescopes can see the star in the sky even when it's daylight, allowing for flexible observations. Hurt said he and his colleagues are hoping to find direct light emissions from the candidate planet in future studies, to confirm its existence.

Vegan planets and aliens are a staple of science fiction through the ages, ranging from Isaac Asimov's "Foundation" series (which began in 1951) to the "Star Trek: The Original Series" episode "The Cage" (created in 1965 and first aired in 1988) to the movies or television shows "Spaceballs" (1987), "Contact" (1997) and "Babylon 5" (1993-98), among many others.

Vega's appeal for science and science fiction is due in large part to its proximity to Earth. Twenty-five light-years is a small jaunt in cosmic terms, given that our Milky Way galaxy alone is roughly 100,000 light-years across. You can easily spot the star with the naked eye, and it rides high in the sky during the summer months of the northern hemisphere as part of the Summer Triangle asterism.

## How Hot is Venus?

Although it is the second planet from the sun, Venus is the hottest planet in the solar system. The reason Venus is hotter than even Mercury is not because of its position in the solar system but because of its thick, dense cloud layer.

A warm blanket

Venus is the planet most similar to the Earth in terms of size and mass, but its atmosphere causes huge differences in the temperatures of the two planets. The distance to Venus from the sun plays only a small role in the cause of its elevated heat wave.

The atmosphere of Venus is made up almost completely of carbon dioxide, with traces of nitrogen. Much of the hydrogen in the atmosphere evaporated early in the formation of Venus, leaving a thick atmosphere across the planet. At the surface, the atmosphere presses down as hard as water 3,000 feet beneath Earth's ocean.

The average temperature on Venus is 864 degrees Fahrenheit (462 degrees Celsius). Temperature changes slightly traveling through the atmosphere, growing cooler farther away from the surface. Lead would melt on the surface of the planet, where the temperature is around 872 F (467 C).

Temperatures are cooler in the upper atmosphere, ranging from (minus 43 C) to (minus 173 C).

Balmy all year-round

Temperatures on Venus remain consistent over time. For one thing, the planet takes 243 Earth days to spin once on its axis (and it spins backwards, at that on Venus, the sun rises in the west and sets in the east). The nights on Venus are as warm as the days.

Venus also has a very small tilt of only 3.39 degrees with respect to the sun, compared to 23.4 degrees on Earth. On our planet, it is the tilt that provides us with the change in seasons the hemisphere slanted closer to the sun feels the heat of spring and summer. The lack of tilt means that even if Venus got rid of its overheated atmosphere, it would still feel fairly consistent temperatures year round.

The lack of significant tilt causes only slight temperature variations from the equator to the poles, as well.