Mercury Sun Transit: Why You Should Watch

If you are into planets and the solar system, then you might want to mark your calendars for this one. The planet Mercury will wander directly in front of the sun, something that only happened about 13 times in a century.

The rare transit will start on Monday, the 9^th of May at 7:12 am EST and is expected to take about 7 ½ hours to fully cross the sun's face at 2:42 pm. According to NASA, most people in Europe and North America should be able to see the event directly through a telescope or ordinary binoculars, if the weather permits. However, people are told to use solar filters before watching the transit. If a solar filter is not available, don't try to look directly at the sun or even use your phone camera for risk of severe damage, vox.com reminded.

Mercury leaves the sun's disk in about 20 mins during today's #MercuryTransit. Here's the transit so far:https://t.co/JPHdKtqE3A

— NASA (@NASA) May 9, 2016

There have been several occasions that planets have appeared in the night sky. Venus is sometimes so bright that ordinary people often think it's an incoming airplane. Mars, on the other hand is so distinct we can even make out its blood red color. And then there's Saturn and Jupiter, well who can miss not seeing them. Aside from the moon, these are the most noticeable objects in the sky. However, Mercury has been found to be practically invisible, except for this week that is.

Since the transit happens less than 15 times every 100 years, here are some of the reasons why you should care. It takes Earth 365 days to make one full course of the sun, which is why our year is measured at those days, and Mars takes 687 days to revolve around the sun. Mercury, on the other hand zooms its way around the sun once every 88 days.

At this speed, it can have more than 4 revolutions for every one the Earth makes. This also means that it is possible to see at least 4 transits by this planet each year. But speed is not the only factor that counts, inclination also matters. For a transit to happen, the sun, Mercury, and Earth have to be directly aligned, Time reported.

The Earth orbits the sun while staying roughly in the sun's equatorial plane. But Mercury's orbit is inclined by about 7 degrees compared to Earth's meaning that most of the time it passes the sun, it appears to be moving below or above it too, eliminating the transit effect. It is only when Mercury's orbital plane intersects Earth's orbital plane that a transit becomes visible to us-which is what's happening now.

A transit also matters because Mercury is one difficult planet to study. The U.S and other countries have been sending spacecraft at planets all over the solar system for years with Mars buzzing with active probes. But experts have always found it brutally difficult to get to Mercury. When you're firing a probe so deep into the gravity well of the sun and aiming at a target moving 30 miles per second (48 k/s) there are a lot more ways for things to go wrong than right. It's for that reason that Mercury has been visited only twice: a flyby by the Mariner 10 spacecraft in 1973, and an orbital mission by the MESSENGER probe, which circled the planet from 2011 to 2015. There are no current plans for NASA or any other space agency to go back.

So remember the little planet today, make sure your lenses are properly filtered because by late afternoon, it will be goodbye time.