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What is it?
Asteroid 2017 BW is a small rocky body that orbits around the Sun every 1.2 years. It is known as a near-Earth object, or NEO, because it passes within 1.3 AU of the Sun (1 AU is the average distance between the Sun and Earth). It’s also an Apollo asteroid meaning its orbit is slightly larger than Earth’s and crosses Earth's path. Don’t worry, as the orbit of 2017 BW is also slightly more tilted than the Earth's, it isn’t on a collision course with our planet.
2017 BW was discovered at Piszkesteto Observatory in Hungary (near the capital of Budapest) on 19 January 2017.
Why is it exciting?
2017 BW has been chosen as a possible target for NASA’s Near-Earth Object Human Space Flight Accessible Targets Study (NHATS), whose purpose is to identify NEOs that may be accessible by future human space flight missions! To help with this, we’re trying to discover as much as we can about this asteroid.
Where is it?
In February 2017, the asteroid reaches its closest point to Earth in almost 100 years, coming within 1.1 million miles (0.012 AU), about 4.6 times further from Earth than the Moon. The close approach provides a fantastic opportunity for us to take detailed pictures and learn more about our newly discovered cosmic neighbor.
What do we know…about its size?
From its brightness, we can estimate that 2017 BW is about 70 m (230 feet) across. However, this estimate is somewhat uncertain, since the asteroid will appear the same brightness if it is big and dark (like coal or tarmac) or small and reflective.
…about its motion?
It’s estimated that the asteroid rotates every 19 hours. That would make 2017 BW’s ‘day’ just 5 hours shorter than the Earth’s.
…about its shape?
The changes in brightness as 2017 BW rotates tell us that the asteroid must be elongated (like a potato) and not round. It appears brighter or dimmer depending on whether we see it large side-on or small end-on; when more reflective surface is on display the asteroid appears brighter.
What do we want to learn?
One of the things that we hope to learn through observations taken with Asteroid Tracker is 2017 BW’s exact rotation rate. We can do this by taking lots of images of the asteroid as it moves across the sky and measuring the brightness as it changes with time.
Who else is watching?
Astronomers at NASA’s Goldstone Solar System Radar (part of the Deep Space Network) in California bounced radar beams off the asteroid when its viewing angle was best from the Earth on 11-13 February 2017.
In the same way that air traffic control radars can give the precise position and speed of airplanes, the planetary radar measurements will be able to give us very precise measurements 2017 BW and improve our knowledge of its orbit, helping to predict where it will be in the future and whether its chance of hitting the Earth will change due the gravity of the Earth pulling on the NEO as it passes close by.
The planetary radars will also be able to make detailed images of 2017 BW, which will allow us to get a much more precise measurement of the size and shape of the asteroid. These observations will also allow us to look for satellites in orbit around the asteroid.