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Frequently Asked Questions


What are exoplanets?

Exoplanets are simply planets that are not in our own solar system. While there are some exoplanets that do not orbit around stars, those are extremely difficult to find. What scientists primarily look for is exoplanets orbiting around a star, the way our planets orbit around our own Sun.

How do we find exoplanets?

Humans have been discovering exoplanets since the early 1990s. So far, we have three main methods that we use to find exoplanets:

Radial Velocity: When objects orbit each other, the smaller doesn't simply go around the larger. The smaller actually pulls a bit on the larger, just like the larger pulls on the smaller. The point that they orbit around is called the "barycentre," or common centre of mass. When looking for planets around other stars, scientists look for shifts in light coming from the star that would indicate an object (like a planet) is orbiting it. Check out this video for more information.

Direct Imaging: Exactly what it sounds like, this method involves taking actual images of the exoplanets using large telescopes. This is very difficult to accomplish, as stars are very far away and often planets can be quite small.

Transits: This is by far the most common way to discover exoplanets, as even relatively small telescopes can accomplish this. When planets orbit stars, they occasionally eclipse their star, or pass between us and their own star. When they eclipse their star, we see less light coming from the star (just like when our moon eclipses the Sun). We can measure the amount of light coming from a star to determine if an object is passing in front of it. This is the method we are using in our project.

Why do we need a certain brightness of star and a certain depth of transit?

Our telescope is pretty small, only 16" (about 40cm) in diameter. Hubble Space Telescope is a whopping 8 ft (2.4m) in diameter! Our little scope can't see as much as some of the bigger ones. That's why we need relatively bright stars. In addition, since our telescope is on Earth and not in space, we have to take all our photos through the atmosphere. The atmosphere causes big fluctuations in the light we see, so we need deep transits (transits with bigger planets, generally) to be able to see a significant drop in brightness once the transit begins.

What is Right Ascension and Declination, and why are they important?

This is like GPS units for stars. It'll tell us where to look in the sky for the target star when we are programming the telescope.

What about Elevation or Altitude and Azimuth?

While RA and Dec tell us where the star is ultimately throughout the sky, Altitude and Azimuth tell us where the star will be compared to the horizon. This allows us to ensure the target star will be above the horizon all night long.

What are Julian Days?

Julian days are a unit of measurement that allows astronomers to avoid dealing with time zones. The Julian calendar simply counts individual days since the start of the Julian period, on January 1st, 4713 BC at 12 midnight (Universal Time). As the Julian Date system counts individual days as a single whole number, each day is divided into decimals following a whole number. For example, September 4th, 2019 at 1:21pm EDT is JD 2458731.1415278. It is 2, 458, 731 days after January 1st, 4713 BC. The numbers after the decimal show how far along the day is.

Using this format makes it easier to do math with time, since a day is divisible by 1000 instead of 24, then 60, then 60 again. It's like using metric distance (1m = 100cm = 1000mm, etc) instead of imperial distance (1mi = 5280ft = 63360in), except with time!

Find today (or any day)'s Julian Date here!

What is the purpose of all these different date and time units (local time, Universal Time (UTC), JD)?

It's all well and good to think of a day as a single unit and then divide it by 1000, especially when telescopes think that way. But humans don't; they think in hours, minutes and seconds, and not only that, but the hours, minutes and seconds related to the area they are closest to. 5 o'clock in Toronto is 6 o'clock in Halifax and 2 o'clock in Vancouver. For us, local time makes the most sense.

But how do we make local time connect with Julian days, for the sake of programming the telescope? We have to choose one spot on Earth and make the Julian days relative to that, and so we have. That's Coordinated Universal Time (or UTC). It is (within 1 second of) mean solar time at 0 degrees latitude. That is to say, it is the time at an arbitrary point on the Earth. That way, we all have something we can compare time to!

What is a Meridian Flip or Meridian Cross?

As stars appear to move from one side of the sky to the other overnight, the telescope may need to flip upside down. This is often because certain telescopes may not physically be able to follow the object the whole way due to risk of collision. To watch a meridian flip and find out a bit more from RASC member Larry McNish, click here.

?My trendline won't work. How do I make it line up with the data

Check out this forum post. They have some tips on settings to change and where to change them that may help!

Last modified: 
Saturday, December 18, 2021 - 3:05am