close approach to earth

The Zen of Space: Comet Hyakutake

Discovered by amateur astronomer Yuji Hyakutake in January 1996, Comet Hyakutake made a close approach to earth in March 1996. Highly visible even in daylight, the comet put on an amazing visual and photographic spectacle. The comet’s remarkable tail is 360 million miles long, the longest known for any comet.

Close Encounter with M44 : On Monday, January 26, well-tracked asteroid 2004 BL86 made its closest approach, a mere 1.2 million kilometers from our fair planet. That’s about 3.1 times the Earth-Moon distance or 4 light-seconds away. Moving quickly through Earth’s night sky, it left this streak in a 40 minute long exposure on January 27 made from Piemonte, Italy. The remarkably pretty telescopic field of view includes M44, also known as the Beehive or Praesepe star cluster in Cancer. Of course, its close encounter with M44 is only an apparent one, with the cluster nearly along the same line-of-sight to the near-earth asteroid. The actual distance between star cluster and asteroid is around 600 light-years. Still, the close approach to planet Earth allowed detailed radar imaging from NASA’s Deep Space Network antenna at Goldstone, California and revealed the asteroid to have its own moon. via NASA

What’s Up for May 2016?

What’s Up for May? Two huge solar system highlights: Mercury transits the sun and Mars is closer to Earth than it has been in 11 years.

On May 9, wake up early on the west coast or step out for coffee on the east coast to see our smallest planet cross the face of the sun. The transit will also be visible from most of South America, western Africa and western Europe.

A transit occurs when one astronomical body appears to move across the face of another as seen from Earth or from a spacecraft. But be safe! You’ll need to view the sun and Mercury through a solar filter when looking through a telescope or when projecting the image of the solar disk onto a safe surface. Look a little south of the sun’s Equator. It will take about 7 ½ hours for the tiny planet’s disk to cross the sun completely. Since Mercury is so tiny it will appear as a very small round speck, whether it’s seen through a telescope or projected through a solar filter. The next Mercury transit will be Nov. 11, 2019.

Two other May highlights involve Mars. On May 22 Mars opposition occurs. That’s when Mars, Earth and the sun all line up, with Earth directly in the middle.

Eight days later on May 30, Mars and Earth are nearest to each other in their orbits around the sun. Mars is over half a million miles closer to Earth at closest approach than at opposition. But you won’t see much change in the diameter and brightness between these two dates. As Mars comes closer to Earth in its orbit, it appears larger and larger and brighter and brighter. 

During this time Mars rises after the sun sets. The best time to see Mars at its brightest is when it is highest in the sky, around midnight in May and a little earlier in June. 

Through a telescope you can make out some of the dark features on the planet, some of the lighter features and sometimes polar ice and dust storm-obscured areas showing very little detail.

After close approach, Earth sweeps past Mars quickly. So the planet appears large and bright for only a couple weeks. 

But don’t worry if you miss 2016’s close approach. 2018’s will be even better, as Mars’ close approach will be, well, even closer.

You can find out about our #JourneytoMars missions at, and you can learn about all of our missions at

Make sure to follow us on Tumblr for your regular dose of space:

New comet Jacques may pass 8.4 million miles from Venus this July

Congratulations to Cristovao Jacques and the SONEAR team!  On March 13 they snared C/2014 E2 (Jacques) in CCD images taken with a 0.45-meter (17.7-inch) wide-field reflector at the SONEAR (Southern Observatory for Near Earth Asteroids Research) observatory near Oliveira, Brazil. A very preliminary orbit indicates its closest approach to the sun will occur on June 29 at a distance of 56 million miles followed two weeks later by a relatively close flyby of Venus of 0.09 a.u. or  8.4 million miles (13.5 million km). If a comet approached Earth this closely so soon after perihelion, it would be a magnificent sight. Of course, watching from Venus isn’t recommended. Even if we could withstand its extreme heat and pressure cooker atmosphere, the planet’s perpetual cloud cover guarantees overcast skies 24/7.

Image credit: Rolando Ligustri

Asteroid to Pass Near Earth on Halloween

This Halloween, the Earth will have a visitor nearly on its doorstep. But it won’t be looking for candy or tossing an egg at our windows—it’s asteroid 2015 TB145, and its flyby, while close, is no reason to be scared.

The visitor was discovered earlier this month with the help of the University of Hawaii’s Pan-STARRS-1 telescope, part of NASA’s Near-Earth Object (NEO) Program, and is an unexpected boon to asteroid researchers.

“Every close-up view of an asteroid tells us more about their structure and composition, information we will need to someday deflect a real threat”, says Department of Earth and Planetary Sciences Curator Denton Ebel.

Since TB145 will be passing the Earth just a little farther than the orbit of the Moon—almost close enough to shout “trick or treat!”—researchers are aiming to learn everything they can about the 400-foot-wide object while the chance presents itself. It likely won’t be visible to the naked eye, but NASA is preparing to get high-resolution looks at the object as it nears Earth using radar and optical imaging.

“The close approach of 2015 TB145 at about 1.3 times the distance of the Moon’s orbit, coupled with its size, suggests it will be one of the best asteroids for radar imaging we’ll see for several years,” Lance Brenner, the head of NASA’s asteroid research program, said in a statement. The unexpected viewing is a great chance to learn more about asteroids, as the next appearance of an object of comparable size so close to Earth is not anticipated until 2027.

Until then, the Museum offers plenty of other ways to learn about asteroids, including a new series of video explainers featuringDr. Ebel. You can view the latest, which details the largest asteroids to ever hit the Earth, below:

Learn more about near-earth asteroids. 

Hubble takes Mars portrait near close approach

Bright, frosty polar caps, and clouds above a vivid, rust-colored landscape reveal Mars as a dynamic seasonal planet in this NASA Hubble Space Telescope view taken on May 12, 2016, when Mars was 50 million miles from Earth. The Hubble image reveals details as small as 20 to 30 miles across.

The large, dark region at far right is Syrtis Major Planitia, one of the first features identified on the surface of the planet by seventeenth-century observers. Christiaan Huygens used this feature to measure the rotation rate of Mars. (A Martian day is about 24 hours and 37 minutes.) Today we know that Syrtis Major is an ancient, inactive shield volcano. Late-afternoon clouds surround its summit in this view.

A large oval feature to the south of Syrtis Major is the bright Hellas Planitia basin. About 1,100 miles across and nearly five miles deep, it was formed about 3.5 billion years ago by an asteroid impact.

The orange area in the center of the image is Arabia Terra, a vast upland region in northern Mars that covers about 2,800 miles. The landscape is densely cratered and heavily eroded, indicating that it could be among the oldest terrains on the planet. Dried river canyons (too small to be seen here) wind through the region and empty into the large northern lowlands.

South of Arabia Terra, running east to west along the equator, are the long dark features known as Sinus Sabaeus (to the east) and Sinus Meridiani (to the west). These darker regions are covered by dark bedrock and fine-grained sand deposits ground down from ancient lava flows and other volcanic features. These sand grains are coarser and less reflective than the fine dust that gives the brighter regions of Mars their ruddy appearance. Early Mars watchers first mapped these regions.

An extended blanket of clouds can be seen over the southern polar cap. The icy northern polar cap has receded to a comparatively small size because it is now late summer in the northern hemisphere. Hubble photographed a wispy afternoon lateral cloud extending for at least 1,000 miles at mid-northern latitudes. Early morning clouds and haze extend along the western limb.

This hemisphere of Mars contains landing sites for several NASA Mars surface robotic missions, including Viking 1 (1976), Mars Pathfinder (1997), and the still-operating Opportunity Mars rover. The landing sites of the Spirit and Curiosity Mars rovers are on the other side of the planet.

This observation was made just a few days before Mars opposition on May 22, when the sun and Mars will be on exact opposite sides of Earth, and when Mars will be at a distance of 47.4 million miles from Earth. On May 30, Mars will be the closest it has been to Earth in 11 years, at a distance of 46.8 million miles. Mars is especially photogenic during opposition because it can be seen fully illuminated by the sun as viewed from Earth.

The biennial close approaches between Mars and Earth are not all the same. Mars’ orbit around the sun is markedly elliptical; the close approaches to Earth can range from 35 million to 63 million miles.

They occur because about every two years Earth’s orbit catches up to Mars’ orbit, aligning the sun, Earth, and Mars in a straight line, so that Mars and the sun are on “opposing” sides of Earth. This phenomenon is a result of the difference in orbital periods between Earth’s orbit and Mars’ orbit. While Earth takes the familiar 365 days to travel once around the sun, Mars takes 687 Earth days to make its trip around our star. As a result, Earth makes almost two full orbits in the time it takes Mars to make just one, resulting in the occurrence of Martian oppositions about every 26 months.