Category: Guide to Space

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The volume of Venus is 9.38 x 10¹¹ km³.

That sounds like a big number, and it is. Here’s the long version: 938,000,000,000 cubic kilometers. Just for comparison, the volume of Venus is 86% the volume of the Earth. That’s why many scientists consider Venus to be the twin planet to Earth. Of course, when you consider that the temperature on the surface of Venus is hot enough to melt lead, and atmospheric pressure is 92 times what you would experience on Earth, and Venus doesn’t exactly seem like Earth’s twin.

Of course, the volume of Venus is just a tiny fraction of the volume of the Sun. You could fit 1.5 million planets the size of Venus inside the Sun and still have room to spare.

It’s hard to study the interior of Venus, but scientists think that the volume of Venus is very similar to the volume of the Earth. The planet has a core of liquid metal surrounded by a mantle of molten rock. This is covered by a crust of solid rock.

Want to know about other objects in the Solar System? Here’s the volume of the Moon, and the size of the Sun.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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The size of a planet is measured in many ways: mass, volume, equatorial diameter, and surface area are the most common. In this article we are going to explore each of these ways to express the size of Venus and a few interesting facts about our close neighbor.

Venus has a diameter that is about 95% of Earth’s. It is 12,100 km across. The Venusian surface area is around 90% of our own at 4.6×10⁸ km². The planet has a volume of 9.38×10¹¹ km³. That puts it a little over 85% of Earth’s volume. One final way to measure the size of Venus is to consider its mass. It has a mass of 4.868 x 10²⁴ kg., just over 81% of Earth’s. These physical characteristics have led many scientists to call Venus the sister planet of Earth.

Size characteristics are the only things that Earth and Venus have in common. At 462°C, Venus has an average temperature that is 410°C higher than the hottest deserts on Earth. The temperature on the Venusian surface can melt lead. You have to be 50 km from the surface to find temperatures that are anything like here on Earth.

Temperature is not the only extreme on Venus. The atmosphere would prevent any life as we know from surviving. To start with, the atmospheric pressure is 92 times that of Earth. It is choked with volcanic ash, sulfuric acid clouds, and is made of 95% carbon dioxide. There are constant hurricane force winds churning the atmosphere. Sustained winds in excess of 360 kph are always present. The conditions on the planet are so extreme that probes can only last a few hours.

The surface shows over 1000 volcanoes or volcanic remnants that are over 20 km in diameter. There are no small impact crater, because the atmosphere is too thick to allow small objects to penetrate to the surface. Scientists believe that the entire surface of the planet was been replaced by volcanic activity 300 to 500 million years ago.

Venus has been visited by spacecraft several times. NASA sent Mariner 2 in 1962. It was the first spacecraft to send information from another planet. The Soviet space program landed Venera 7 in 1970. It was the first spacecraft to land on another planet. NASA’s Magellan mapped 98% of the surface in the early 1990s and the European Space Agency currently has the Venus Express in orbit studying the planet’s atmosphere. In all, we have gained a great deal of information about this inhospitable planet in the last 30 years.

Want to know the size of other planets in the Solar System. Here’s an article about the size of Jupiter, and here’s an article about the size of Saturn.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

References:
http://www.nasa.gov/audience/forstudents/5-8/features/F_The_Planet_Venus_5-8.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=OverviewLong
http://en.wikipedia.org/wiki/Venus

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The radius of Venus is 6,052 km. Double that and you get the diameter of Venus: 12,104 km.

Need some comparison? The equatorial radius of Earth is 6,378 km, so the radius of Venus is 95% the Earth’s radius. With such a similar size, you can see why Venus is considered Earth’s twin planet (evil twin, really, when you consider it’s hot enough at the surface to melt lead, with an atmosphere 92 times as thick as Earth).

With other planets in the Solar System, we talk about their equatorial and polar radii. That’s because most planets are rotating on their axis so quickly they’re a little flattened out, with a bulge around the equator. For example, here on Earth, points at the equator are actually 7 km further from the center of the Earth than the poles.

Venus, on the other hand rotates so slowly on its axis that it isn’t flattened out at all. While Earth takes 24 hours to complete one rotation, Venus takes 243 days to spin once on its axis (it also rotates backwards compared to the other planets in the Solar System, but that’s another story).

So the radius of Venus is 6,052 km, whether you calculate it from the center to the equator, or the center to the poles.

Want to know the radius of other planets? Here’s an article about the radius of Mercury, and here’s an article about the radius of the Moon.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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The mass of Venus is 4.868×10²⁴ kg. That is about 82% of the mass of Earth. Alright, end of story and thank you for reading. Okay, we would never do that to you here at Universe Today. There are far too many interesting facts about Venus to leave you hanging like that.

Here are a few other physical characteristics of the second rock from the Sun:

Diameter	12,100 km
Surface Gravity	8.87m/s2
Surface Area	460,000,000 km2
Volume	9.38×1011km3
Surface Atmospheric Pressure	92 times that of Earth
Average Surface Temperature	462 degrees Celsius
Rotation	Retrograde
Density	5.204 g/cm3

Scientists believe that the high mass and density of Venus can be accounted for by its high concentration of rock and metals. They believe that the planet has a liquid metallic core that is surrounded by a molten rock mantle. Actual proof of this is nearly impossible since the reflective nature of the planet’s atmosphere makes many types of observation impossible.

Venus was once thought to be a dead planet. There is no life on the surface for many reasons, but recent study of the surface has revealed that there may be active volcanoes on the planet. That means that it is alive, geologically speaking. Previously, scientists had known that the planet had been resurfaced by volcanic activity 300 to 500 million years ago, but had thought that the activity died out during that same time frame.

There have been many missions sent to Venus. The Soviet space program started the race to Venus with the Venera program. It is hard to tell exactly how many Soviet missions to Venus were launched since the program would not announce a probe that failed, but more than a dozen were successful. NASA launched several mission of its own. Early missions from both programs failed because neither was prepared for the extreme pressure within the Venusian atmosphere. Even those that were able to transmit from the surface could only survive for less than one hour.

The Venus Express is currently in orbit around Venus. BepiColumbo is set to launch in 2014. It is hoped that the Akatsuki probe can reawakened to gather information when it arrives in the area in 2016 and the Venus In-Situ Explorer is in the planning stages. Scientists are determined to unravel the planet’s mysteries. Like you, they want to know more than the mass of Venus.

Here’s an article about the mass of Mercury, and here’s an article about the mass of the Earth.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

References:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=Facts
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=OverviewLonghttp://solarsystem.nasa.gov/planets/profile.cfm?Object=Venus&Display=Educ

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Although it’s similar in size, Venus is very different from Earth. The temperature at the surface is hot enough to melt lead, with an atmosphere of almost pure carbon dioxide, 92 times thicker than Earth’s atmosphere. Even with this extreme environment, is it possible that there’s life on Venus?

Probably not.

Here on Earth, we find life wherever we find liquid water: kilometers deep underground, beneath glaciers, and even inside nuclear reactors. If there’s liquid water, there’s life. But there doesn’t seem to be any liquid water on Venus.

Scientists think that Venus did have liquid water billions of years ago, but a runaway greenhouse effect heated up the planet to the point that all the water evaporated, and was eventually lost to space. The atmosphere is now 96% carbon dioxide, with the rest nitrogen and a few other trace compounds.

But there’s another possibility. High up in the atmosphere of Venus, at an altitude of 50 km, the air pressure and temperature get to the point that they’re very similar to Earth. In fact, at this altitude, it’s the most Earthlike place in the whole Solar System. Some scientists think that there could be microbial life high up in the atmosphere of Venus.

Since the Sun’s solar wind is constantly blowing on Venus, and Earth is “downwind” from Venus, it’s possible that microbial life is being blown from Venus to Earth. Maybe life on Earth got its start on Venus.

You can read a longer article about the possibility of life on Venus here. And here’s a video that shows how the atmospheres of Venus and Mars leak into space.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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When you look at the Moon and Mercury, their surfaces are pounded with impact craters. Mars has many craters, and even Earth has its share. But what about Venus, are there craters on Venus?

There are craters on Venus, but not many. The Solar System is relatively empty now, but less than a billion years after the formation of the Solar System, there were still many objects left over. These crashed into planets and moon, during a time scientists call the late period of heavy bombardment. Many of the craters on Mercury and the Moon were formed during that time.

Strangely, Venus shows no record of the heavy bombardment period. Either it didn’t get struck, which is unlikely, or some process resurfaced the planet, removing all traces of the impact craters. The resurfacing process stopped at some time in Venus’ more recent history. And so, all the craters that scientists do see on the surface of Venus are relatively young.

Craters on Venus are different from craters on other planets. The planet’s thick atmosphere stops the smaller objects from even reaching the surface of Venus; they just burn up in the atmosphere. There are about 1000 craters identified on the surface of Venus.

Crater Mead is the largest known crater on Venus, named after the American anthropologist, Margaret Mead. It measures 280 km in diameter, and contains several concentric rings.

We have written many articles about Venus on Universe Today. Here’s an article about the evolution of Venus’ surface, and here’s a “Where in the Universe” challenge featuring a crater on Venus.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

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Like all the planets, Venus formed approximately 4.6 billion years ago when the Sun and the Solar System came out of the solar nebula. So, the age of Venus is 4.6 billion years old.

Before the Solar System, there was just a large cloud of hydrogen gas in a giant nebula. Some event, like a nearby supernova explosion put a shock into the cloud, and caused it to begin collapsing. Many stars, large and small, formed in this nebula, and one of these went on to be the Sun. As the material condensed together, conservation of momentum caused it to spin up and flatten out.

A protoplanetary disk of material formed around the newborn Sun, and it was here that the planets formed. Dust clumped together to form rocks, rocks smashed together into boulders, and mountain-sized objects became protoplanets. In the first few hundred million years of the age of Venus, it’s likely that the planet was smashed many times by these large asteroid and protoplanets. But eventually, Venus became the dominant object in the region, sucking in everything with its gravity.

We know that Venus was probably the victim of a large collision because it rotates in the opposite direction from the rest of the planets in the Solar System. A large collision could have turned its rotation backwards.

How do we know Venus’ age? We can’t measure the age of Venus directly, because of the intense heat and pressure on the surface of Venus. Instead, scientists measure the age of meteorites that have fallen to Earth. After analyzing hundreds of objects, scientists have found that they all formed at approximately the same time. These meteorites are the leftover pieces from the formation of the Solar System, and help prove that all the objects in the Solar System formed at the same time.

And so we know that the age of Venus is 4.6 billion years old.

We have written many articles about Venus. Here’s one about how life on Venus could be blown to Earth, and here’s an article about how you might keep a Venus rover cool.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s NASA’s Solar System Exploration Guide to Venus.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Venus. Listen to it here, Episode 50: Venus.

Reference:
NASA Solar System’s Big Bang

Positioned north of the ecliptic plane, the constellation of Perseus was one of the original 48 constellations listed by Ptolemy, and endures as one of the 88 modern constellations.adopted by the IAU. It covers 615 square degrees of sky and ranks 24th in constellation size. Perseus contains between 6 and 22 stars in its primary asterism and houses 65 Bayer Flamsteed designated stars within its confines. It is bordered by the constellations of Cassiopeia, Andromeda, Triangulum, Aries, Taurus, Auriga and Camelopardalis. Perseus is visible to all observers located at latitudes between +90° and ?35° and is best seen at culmination during the month of December.

There is one annual meteor shower associated with Perseus and it is one of the most reliable of all – the Perseids. The peak date occurs on or about August 10th of each year and the radiant – or point or origin is near the Double Cluster. The meteoroid stream duration for this meteor shower lasts about five days, with activity beginning one to two days prior to the peak date and ending two or three days afterwards. The Perseid meteor shower has a wonderful and somewhat grisly history. Often referred to as the “Tears of St. Lawrence” this annual shower coincidentally occurs roughly about the same date as the saint’s death is commemorated on August 10. While scientifically we know the appearance of the shooting stars are the by-products of comet Swift-Tuttle, our somewhat more superstitious ancestors viewed them as the tears of a martyred man who was burned for his beliefs. Who couldn’t appreciate a fellow who had the candor to quip “I am already roasted on one side and, if thou wouldst have me well-cooked, it is time to turn me on the other.” while being roasted alive? If nothing else but save for that very quote, I’ll tip a wave to St. Lawrence at the sight of a Perseid! While the fall rate – the number of meteors seen per hour – of the Perseids has declined in recent years since Swift-Tuttle’s 1992 return, the time to begin your Perseid watch is before the peak date of August 12. If you are contending with a Moon which will interfere with fainter meteors, the later you can wait to observe, the better. The general direction to face will be east around midnight and the activity will move overhead as the night continues. While waiting for midnight or later to begin isn’t a pleasant prospect, by then the Moon has gone far west and we are looking more nearly face-on into the direction of the Earth’s motion as it orbits the Sun, and the radiant – the constellation of the meteor shower origin – is also showing well. For those of you who prefer not to stay up late? Try getting up early instead! How many can you expect to see? A very average and cautiously stated fall rate for this year’s Perseids would be about 30 meteors per hour, but remember – this is a collective estimate. It doesn’t mean that you’ll see one every two minutes, but rather you may see four or five in quick succession with a long period of inactivity in between. You can make your observing sessions far more pleasant by planning for inactive times in advance. Bring a radio along, a thermos of your favorite beverage, and a comfortable place to observe from. The further you can get away from city lights, the better your chances will be.

The long “Y” shape of Perseus has a long and colorful mythological history. Perseus was conceived in a golden rain and he and his mother were cast into the sea in a chest – left to die. His mother prayed to Zeus for deliverance and they were rescued by a fisherman who raised Perseus as his son. Eventually the king, in trying to rid himself of Perseus, demanded horses as a wedding present. Knowing Perseus had none, he chose the head if Medusa instead. With the aid of the gods, Perseus defeated Medusa – and from her body sprang Pegasus, the winged horse. As the story goes, he then to flight to the lands of king Cepheus, where he then continued his saga with Cassiopeia and Andromeda – rescuing the maiden from the Cetus, the sea monster. This is why, according to legend, you find all of these constellations so close together in the sky… and Perseus is depicted holding the head of Medusa, whose most famous star – Algol – represents the eye of the demon.

Let’s begin our binocular tour with a look a the “Demon Star” – Beta Persei – the “B” symbol on our map. Beta Persei (RA 03 08 10 Dec +40 57 20) and it is the most famous of all eclipsing variable stars. Ancient history has given this star many names. Associated with the mythological figure Perseus, Beta was considered to be the head of Medusa the Gorgon, and was known to the Hebrews as Rosh ha Satan or “Satan’s Head.” Seventeenth century maps labeled Beta as Caput Larvae, or the “Specter’s Head,” but it is from the Arabic culture that the star was formally named. They knew it as Al Ra’s al Ghul, or the “Demon’s Head,” and we now know it as Algol. Because these medieval astronomers and astrologers associated Algol with danger and misfortune, we are led to believe that Beta’s strange visual variable properties had been noted throughout history. Italian astronomer Geminiano Montanari was the first to record that Algol occasionally “faded,” and its regular timing was cataloged in 1782 by John Goodricke, who surmised that it was being partially eclipsed by a dark companion orbiting it. Thus was born the theory of the eclipsing binary, which was proved spectroscopically for Algol in 1889 by H. C. Vogel. Located 93 light-years away from Earth, Algol is the nearest eclipsing binary, and is treasured by the amateur astronomer because it requires no special equipment to easily follow its stages. Normally Beta Persei holds a magnitude of 2.1, but approximately every three days it dims to magnitude 3.4 and gradually brightens again. The entire eclipse only lasts about 10 hours! Although Algol is known to have two additional spectroscopic companions, the true beauty of watching this variable star is not telescopic – but visual.

Now, let’s use our binoculars and head for Alpha Persei – the “a” symbol on our map. The brightest star of this constellation is also called Mirfak . It is a supergiant star of stellar spectral type F5 Ib with an apparent brightness of 1.79 magnitude and resides at a distance of about 590 light-years. Is it big? You bet. Mirfak is about 62 times larger than our Sun and shines 5000 times brighter, but the beauty is in the field. If you’ve noticed that Alpha is in a group of stars, you’ve noticed right. It’s called the Alpha Persei Association. Viewable with the unaided eye, but best in binoculars, this young, moving star cluster is also known as Melotte 20 or Collinder 39 and is around 601 light years away. Brightest members include Alpha, Delta, Epsilon, Psi, 29, 30, 34 and 48 Persei.

Keep your binoculars handy as we head off to NGC 869 and NGC 884 – the “Double Cluster”. These two open stars clusters (NGC 869 (RA 02:19.1 Dec +57:09) and NGC 884 (RA 02:22:0 Dec +57:08) are perhaps the most beautiful objects of the night sky for binoculars and small, rich field telescopes. Both lie at distances of more than 7,000 light years and are separated by several hundred light-years. Often seen by the unaided eye as a hazy patch in the winter Milky Way, the clusters were first recorded by Hipparchus, but have likely been known since antiquity. NGC 869 is considered to be as much as 19 million years old and this OB1 association sometimes is called Chi Persei. Its companion, NGC 884 is nearer to 12 million years old and is dominated by bright blue stars which notes its youth. Also look for a smattering of orange stars in larger telescopes!

Ready to get Messier? Then locate Messier 34 (RA 02:42:1 Dec +42:46). In binoculars, M34 will show around a dozen fainter stars clustered together, and perhaps a dozen more scattered around the field. Small telescopes at low power will appreciate M34 for its resolvability and the distinctive orange star in the center. Larger aperture scopes will need to stay at lowest power to appreciate the 18 light-year span of this 100 million year old cluster, but take the time to power up and study. You will find many challenging doubles inside!

Now hop on to NGC 1342 (RA 3:31.6 Dec +37:20). Holding a respectable magnitude 7 and covering about 14 arc minutes of sky, this small, compressed, open cluster of stars is well within binocular and small telescope range. It’s been studied for galactic disc metallicity and is on many binocular and deep sky observing lists.

How about two more galactic star clusters? Then try your hand at NGC 1545 (RA 4:20:9 Dec +50:15). It’s around 6th magnitude, but at 18 arc minutes in size will require at least a small telescope to separate it from the starry background. It has been studied for universality of initial mass function of open star clusters. More northern NGC 1528 (RA 4:15:4 Dec +51:14) is about the same magnitude, but a little larger and is also known as Herschel 61, Collinder 47 and Melotte 23.

What about NGC 1499? NGC 1499 (RA 04:00:07 Dec +36:37) is the “California Nebula”. If you’re able to view under very dark skies, the California Nebula can be seen unaided and in binoculars, but its low surface brightness makes it tough for a telescope. NGC 1499 is probably illuminated by Xi Persei, a hot blue-white main sequence star of spectral type O7e. This star belongs to an association of young stars which probably arose from this interstellar cloud, the Perseus OB2 association. What a great opportunity for astrophotographers!

You can also try IC 348 (RA 3:44.5 Dec +32:17). This open star cluster with nebulosity has an apparent magnitude of 7 – but that doesn’t mean it’s bright or easy. It’s a very faint reflection nebula that’s going to require perfect conditions and probably the aid of a nebula filter, too. The “Flying Ghost” has been the subject of many studies, including the search for outflows and protostars. In 2006, the Spitzer Space Telescope turned an eye its way to find disc-less T-Tauri type stars as well as thosel as surrounded by thick, primordial disks. Why is that important? “The disk longevity and thus conditions for planet formation appear to be most favorable for the K6-M2 stars, which are objects of comparable mass to the Sun for the age of this cluster.”

There are many other wonderful deep sky objects in Perseus, so get a good star chart and enjoy the “Hero”!

Sources:
Chandra Observatory
Wikipedia
Chart Courtesy of Your Sky.